In view of the recent preparation of cholera toxin crystals, additional support is sought to extend the structure analysis of molecular interactions at the cell surface to include the crystallographic structure determination of the cholera toxin and complexes of the cholera toxin (or choleragenoid) with the specifying oligosaccharide moiety of the ganglioside receptor. Electron microscopy of ordered arrays of cholera toxin are also proposed in order to establish the mode of interaction with the membrane as a prerequisite to understanding the toxin's role in transmembranal signaling of adenylate cyclase and the consequent stimulation of cAMP sensitive chloride pump.